This application is based upon and claims priority to German Patent Application 199 51 460.7 filed Oct. 26, 1999.
The invention relates to a pipe connection with a connecting member, a nut and a pipe having a formed-on connecting portion. The pipe is clamped in between the nut and the connecting member.
DE 195 11 063 A1 describes a pipe connection where the connecting portion is clamped between the conical bore of the nut and the conical bore of the connecting member. The members form a first and a second tensioning face. Both tensioning faces are formed in such a way that they rest in a planar way against the conical bore of the connecting member and the conical bore of the nut respectively. Furthermore, an annular contact shoulder is provided to limit the tightening operation. A pipe projection is arranged in front of the first tensioning face cooperating with the conical bore of the nut. The pipe projection, by means of a region of transition, ends in the tensioning face. The remaining annular space is intended to receive a soft seal which, in particular, is to achieve precision sealing.
The length of contact between the first tensioning face of the connecting portion of the pipe associated with the connecting member and the conical bore of the connecting member in the tightened condition extends over a large part of the axial length of the conical bore of the connecting member. If a soft seal is provided, it is possible that the seal may be damaged while the pipe is being slid into the conical bore of the connecting member. Furthermore, the space available for the soft seal is so limited that only a very thin ring can be used which is very sensitive to external influences.
DE 195 20 099 C2 illustrates a pipe connection which also comprises a connecting member with a conical bore as well as a nut. A pipe is clamped between the two by a connecting portion. The connecting portion of the pipe includes a first supporting face which extends substantially radially relative to the longitudinal axis of the connection. The supporting face, in the tightened condition, is axially supported on the end face of the connecting member. Furthermore, the connecting portion includes a tensioning face which is designed to cooperate with and match the conical bore of the nut. A cylindrical pipe portion is arranged in front of the connecting portion. The cylindrical pipe portion starts from the radially extending supporting face and extends into the circular cylindrical bore following the conical bore of the connecting member. A seal is positioned in the annular space between the outer face of the pipe projection, the supporting face of the connecting portion and the conical bore of the connecting portion. The disadvantage of this design is that the connection cannot be used without a soft seal. In addition, when fitting the pipe to the connecting member, the soft seal runs the risk of being damaged.
It is an object of the present invention to provide a pipe connection with full planar contact. The metallic sealing effect is improved. Also, it is additionally possible to use a soft seal which is less likely to be damaged.
In accordance with the invention, a pipe has a connecting member. The connecting member includes a first end face; a first conical bore starting to taper from the first end face, which defines a first cone angle and an axial bore length; a circular cylindrical bore adjoining the first conical bore; and an outer face having a threaded portion. A nut is included for the pipe connection. The nut includes a threaded bore which matches the threaded portion of the connecting member; a second conical bore following the threaded bore and tapering in a direction opposite to the first conical bore of the connecting member and defining a second cone angle; and a through bore. A pipe is included in the pipe connection. The pipe is guided through the through-bore of the nut. The pipe defines a longitudinal axis and has a cylindrical pipe projection extending into the circular-cylindrical bore of the connecting member. A connecting portion is formed on the pipe. The connecting portion follows the pipe projection and includes a first conical tensioning face cooperating with the first conical bore of the connecting member. The connection portion defines a third cone angle. The third cone angle is greater than the first cone angle of the first conical bore. The axial length of the connecting portion which overlaps with the first conical bore is smaller than 15% of the axial bore length of the first conical bore. The connecting portion includes a second conical tensioning face which co-operates with the second conical bore. The second conical tensioning face defines a fourth cone angle which corresponds to the second cone angle. An annular recess is arranged on the radial inside of the first tensioning face. The annular recess starts from the end positioned in the region of the smallest cone diameter of the first tensioning face and extends over at least part of the axial length.
An advantage of the above arrangement is that as a result of the angular conditions regarding the first cone angle and the third cone angle, an overlap is reached. Thus, metallic contact is ensured even if the conical first tensioning face has a short length. It is also ensured that the connecting member is not subjected to impermissibly high loads due to the annular recess. The first tensioning face is able to deform, at least in a partial region of the length of overlap with the first conical bore of the connecting member. Thus, there is no stress concentration.
In a further advantage, after contact has been established between the radially extending supporting face and the end face of the connecting member, only approximately 30xc2x0 of a rotational path is required to tighten the system. Furthermore, the advantage relative to the prior art assembly, where only a radially extending supporting face co-operates with the end face of the connecting member, is that it is possible to achieve easy and accurate centering of the connecting portion and of the pipe relative to the connecting member. The annular recess can be used to accommodate a soft seal. The seal is centered and accommodated so as to be protected. In addition, as compared to an assembly where the first conical tensioning face of the connecting portion covers approximately the entire axial length of the conical bore of the connecting member, it is possible to use a seal with a greater volume. As compared to the state of the art assemblies, the metallic seal is improved even if a soft seal is not provided. This is due to the fact that as a result of the angular conditions and the short axial length, it is possible to achieve a relatively high surface pressure which is responsible for a correspondingly adequate sealing effect. Advantageous conditions regarding the surface pressure and the sealing effect are achieved if the smallest cone diameter of the first tensioning face is up to 5.5% smaller than the greatest diameter of the first conical bore.
Furthermore, in order to limit the degree of tightening, which ensures that the load on the connecting member is limited to a particularly advantageous ratio, it is proposed that the connecting portion, following the greatest diameter of the first tensioning face, is provided with an annular shoulder. The shoulder extends radially relative to the longitudinal axis. In this embodiment, the advantageous conditions of the surface pressure can be put into effect in those cases where the greatest cone diameter of the first tensioning face, in the region of transition to the annular shoulder, is between 0.15 mm and 0.5 mm greater than the greatest diameter of the first conical bore of the connecting member. The degree of tightening can also be limited if the end face of the pipe projection comes to rest against a step face of the connecting member.
Advantageous strength and deformation conditions for the part of the first tensioning face which comes into contact with the conical bore of the connecting member and for the portion of the connecting portion positioned underneath can be achieved if the annular recess is delimited by the outer face of the pipe projection and by an annular face which starts from the end with the smallest diameter and which is conically tapered in the direction opposed to that of the first tensioning face with a fifth cone angle. It is particularly advantageous if the fifth cone angle ranges between 100xc2x0 and 160xc2x0, and especially amounts to 130xc2x0.
The above design conditions can be particularly advantageously applied to embodiments where the first cone angle is about 24xc2x0 and the second cone angle is about 90xc2x0. These are standardized conditions so that the solution in accordance with the invention can also be advantageously used for standard connections. Advantageous sealing and tightening conditions are achieved if the third cone angle is about 30xc2x0 to 40xc2x0. The fourth cone angle of the second tensioning face, in respect of size, corresponds to the second cone angle and thus preferably amounts to about 90xc2x0.
A soft seal is used to increase sealing in those cases where repeat connections are likely to be more frequent. The soft seal fills the annular recess and projects therefrom into the space delimited by the outer face of the pipe projection and by the first conical bore. The soft seal is protectively received in the annular recess. Thus, during assembly procedures, the risk of damage to the seal is considerably reduced. In addition, this embodiment provides a greater volume to receive the seal. In consequence, the seal can be designed to be more robust.
The axial cone length of the first tensioning face is smaller than 15% of the axial length of the first conical bore to achieve the desired length of overlap in an assembly where an annular shoulder delimits the operation of tightening the connecting portion. Thus, the immersion of the first tensioning face into the first conical bore of the connecting member is at a desired depth. A step is provided at a distance from the annular shoulder to facilitate deformation.
From the following detailed description, taken in conjunction with the drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.